Telephone transmitter



' June 27, 1933.

L. C. POCOCK ET AL TELEPHONE TRANSMITTER Filed May 1930 L.C. POCOCK R BLA CKBURN IN VENTO/PS J TU}? TON ATTORNEY Patented June 27, 1933 UNITED STATES PATENT OFFICE LYNDALL C.

POOOCK, REGINALD BLACKBURN, AND JOHN TUBTON, OF ALDWYCH,

LONDON, ENGLAND, ASSIGNORS TO WESTERN ELECTRIC COMPANY, mcoaroaa'rnn, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK TELEPHONE TRANSMITTER Application filed May 16, 1930, Seria1 No. 452,842, and in Great Britain July 22, 1929;

This invention relates to improvements in telephone instruments and more particularly i nor that the receiver can be held to the ear while the mouthpiece of the transmitter 1s m convenient tothe mouth of the user, the to be understood, however, that the invention is not restricted to instruments of this type.

The principal feature of the invention re lates to a telephone handset of the above type in which speech is adapted to be directed on to a portion of the transmitter diaphragm nearest the mouth of the user in order to obtain the shortest possible speech path. The above effect is conveniently attained by the provision of a mouthpiece, suitably and removably mounted on the transmitter casing, formed that sound waves are which is so directed on to a portion of the diaphragm, other than the centre thereof. I

Another feature of the invention is a dome shaped mouthpiece for'use with a telephone headset transmitter in which a sound channel extends from that part of the outer wall adjacent the mouth of user and which takes the shortest path to the diaphragm.

The mouthpiece is preferably a substantially hollow dome shaped moulding, in which the sound passage formed therein is inclined to the plane of the transmitter diaph agm, and in which a recessed portion or portions is adapted to be closed by a plate in order not to impair the efficiency of the instrument.

The provision ofthis recess or recesses in the interior of the mouthpiece considerably lightens the instrument.

Another feature of the invention is an apertured plate, that is secured to the mouthpiece in such a manner that the aperture is situated opposite a speech channel formed in the mouthpiece, the said plate forming both the closing plate for a recessed portion of the mouthpiece and the sealing plate for the capsule containing the electrodes and diaphragm transmitter being of the granule type. It isassembly, when the mouthpiece is mounted on the transmitter'casing. A further feature of the invention consists in the provision of a thin sheet of cellulose acetate which is inserted in front of the diaphragm for the purpose of protecting the iatter and the transmitter capsule from moisure.

These and other features of the invention will better understood from the following description; but it should be pointed out that although the invention'is described with reference to a handset wherein the transmitter and receiver are mounted on a common handle 1t 1s not necessarily limited thereto, since many of the features of the invention are applicable to other types of instruments.

A particular embodiment of the invention w1ll now be described with reference to the accompanying drawing which is an enlarged sectional View of the transmitter and mouthplece, which is adapted to be associated with :a telephone handset as illustrated and described in British Patent No; 304,843.

' The transmitter casing 1 has secured therein the transmitter capsule 2 inclined in such a position to the plane of the receiver (not shown) that the granules in the chamber 3 tend by gravity to remain in contact with the diaphragm 4 throughout a wide range of angular. positions which the handset may assume. In front of the diaphragm a thin sheet of cellulose acetate 20 approximately of an inch thick is seated upon a ring 21 for preventing moisture from the breath from entering the capsule. The cellulose sheet may erably closed by a grid 9 forming a pluralit of slots across the outer end of. the channe which however, may be left completely open if desired. The mouthpiece is mounted on the 5 transmitter casing 1 in an convenient manner and the inner end of t e channel 8 is directed towards a segment of the diaphragm above its central (point and near the mouth of the talker instea of toward the centre of the 0 dia hragm as has been the previous practice.

. he -funnel or channel 8 occu ies a relatively small portion of the total vo ume of the mouthpiece and the majority of the remaining portion of the interior thereof is cut away in order to make the instrument as li ht as possible. The air cavity 10 so formed 1s prevented from affecting the performance of the mouthpiece by means of a closing plate 11, which also forms the plate for sealin the capsule when the mouthpiece is mounte on the transmitter casing. This plate 11 is" formed -with lugs 12 that secure a rubber ring 13, U-shaped in section, in position when the transmitter is assembled, in order to effect a sound proof joint between the capsule and the mouthpiece.

The closing plate 11 is secured to the mouthpiece by a screw .14 and is provided with a hole 15 opposite the inner end of the tunnel or channel 8 so shaped as to continue the opening smoothly down to the capsule.

From the foregoing description it will thus be appreciated that an hygienic transmitter mouthpiece has been devised wherein the speech is directed to the nearest part of the diaphragm in a simple and expeditious manner and without impairing the efiiciency of the instrument.

It will be understood that althou h the invention has been described with re erence to a transmitter of the type described in British Patent N 0. 304,843, it is equally applicable to other types of transmitters.

What is claimed is:

1. A telephone transmitter in which the mouthpiece thereof is so formed that sound waves are directed only on to an eccentric portion of the transmitter diaphragm which is nearest the mouth of the user in order to obtain the shortest possible speech path.

2. A telephone handset transmitter in which a single sound passage in the mouthpiece of the transmitter is inclined to the. normal to the plane of the transmitter diaphra the walls of said assa'ge being dis ahperforated plate mounted in front of said 5 eet.

4. A telephone'transmitter comprising a casing, a dished dia hragm mounted in said casing, and a thin s eet of cellulose acetate secured infront of thediaphragm to protect the diaphra from moisture.

sembly phragm seated in said 0 cellulose acetate secured cave side of said diaphragm, a perforated guard plate adjacent said film,'an annular washer between said film and said guard com rising a cash g a dished diap athin film of plate, and a sprin ring locking said diaphragm, washer and guard plate in said casing.

6. A telephone transmitter comprising a casing, a diaphragm mounted within said casing, a mouthpiece, secured to'said casing, having a recess and a sound terminating adjacent said diaphragm, said sound passage being inclined to the plane of the diaphragm and so disposed asto direct sound waves to only an eccentric portion of the dia hragm nearest the mouth of the user, an a plate member mounted in said mouthpiece, having an imperforate portion for seallng said recess and an aperture substantially conforming to the inner end of said sound passage.

In witness whereof, we hereunto subscribe our names this fifteenth day of A ril 1930.1

LYNDALL C. PO OCK. REGINALD BLACKBURN.. JOHN TURTON.

acent the con 5. In a te ephone transmitter, a unitary aspose so as to direct soun waves only on to v a rtion of the diaphragm nearest the mouth o the user. V 00 3. A telephone transmitter comprising electrodes and a diaphragm mounted within a capsule secured within the transmitter casing,'a thin sheet of cellulose acetate in front of said diaphragm in.order' to protect the 65 capsule and diaphragm from moisture, and 

